Handheld Doppler Detection and Light Illumination for Vascular Mapping in Nasal Reconstruction.

BACKGROUND: The application of the expanded forehead flap in nasal reconstruction has the advantage of being able to provide a sufficient amount of flap and can provide good aesthetic results. For an expanded forehead flap to survive, there must be adequate arterial supply and venous return. Despite this, limited studies have been conducted on preoperative vascular mapping and the design of the expanded forehead flap for nasal reconstruction. In this article, the authors present a technique of hand-held Doppler detection with light illumination for vascular mapping. PATIENTS AND METHODS: The study included patients who underwent total nasal reconstruction with expanded forehead flaps between May 2016 and April 2021. The design of the flap was based on the result of preoperative vascular detection by hand-held Doppler detection assisted by light illumination. RESULTS: A total of 32 patients underwent total nasal reconstruction with an expanded forehead flap. The distal part of the flap became necrotic 1 week after the surgery in 2 patients. Following dressing changes and the administration of antibiotics, the distal flap in these patients survived well. No complications were reported in the long term. CONCLUSIONS: Hand-held Doppler detection combined with light illumination is a convenient and effective preoperative design method for nasal reconstruction with an expanded forehead flap. All flaps survived well in the long term. LEVEL OF EVIDENCE: Level IV.

Prefrontal NIRS signal is unaffected by forehead Doppler flux during incremental cycling exercise.

Near-infrared spectroscopy (NIRS) is used to measure tissue concentrations of oxyhemoglobin (O2 Hb) and deoxyhemoglobin (HHb). In the context of exercise, NIRS confers a higher signal-to-noise ratio than other neuroimaging techniques. However, part of the signal may be influenced by thermoregulatory hyperemia in the superficial cutaneous capillaries of the forehead. The degree to which NIRS signals during exercise reflect cerebral or extracerebral hemodynamic changes is a continuing source of controversy. However, the influence of skin blood flow may be attenuated depending on the NIRS technique (e.g., frequency domain machines with maximal optode separation distances >3.5 cm). The purpose of this study was to compare the changes in forehead skin blood flow and cerebral hemoglobin concentration during incremental exercise versus direct vasodilation of the forehead skin induced by gradual local heating. Thirty participants (12 females, 18 males; age: 20.8 ± 3.2 years; body mass index: 23.8 ± 3.7 kg·m-2 ) participated in the study. Forehead skin blood flow was quantified laser Doppler flux and absolute concentrations of cerebral O2 Hb and HHb were measured by NIRS. Local heating significantly increased the Doppler flux signal across time and these changes were significantly correlated with skin temperature. During incremental exercise, skin temperature, Doppler flux, O2 Hb and HHb increased however, the only significant change that was consistently correlated with Doppler flux was skin temperature. Therefore, a significant change in forehead skin blood flow may not significantly the NIRS hemoglobin data, depending on the type of NIRS device used.

Transfer Patterns and Clinical Applications of the Forehead Flaps Based on the Supratrochlear Artery and Supraorbital Artery.

This study aimed to describe the application of transferring preexpanded forehead flaps based on the supratrochlear and supraorbital arteries in 3 patterns for facial reconstruction: Pattern I, interpolated flap; Pattern II, island flap; and Pattern III, propeller flap, which was subdivided into direct propeller flap (Pattern IIIa) and indirect propeller flap (Pattern IIIb). During the first stage, a tissue expander was inserted underneath the forehead. After sufficient inflation of the expander, a forehead flap based on the supratrochlear or supraorbital artery was elevated and transferred to reconstruct the facial defects. Three weeks after the surgery, pedicle division was performed, in which Pattern I and Pattern IIIb flaps were used. Twenty-four patients underwent facial reconstruction. Twenty-three flaps survived without any perfusion-related complications. Venous congestion developed in an island flap. All patients were followed up after surgery, ranging from 2 to 156 (mean, 19) months. The color and texture of the flap matched those of the adjacent skin. The patients and their families were satisfied with the final functional and esthetic outcomes. The forehead flap based on the supratrochlear and supraorbital arteries provides reliable coverage of facial defects. The conventional interpolated flap continues to be the most dependable. Single-stage reconstruction using the island flap and direct propeller flap is applicable to patients who decline the pedicle division procedure. The novel technique of using the indirect propeller flap is safe for cheek reconstruction with minimal donor-site morbidity and esthetically pleasing results.

New Insight into Glabellar Arteries: A Three-Dimensional Computed Tomography and Dissection Study.

BACKGROUND: Vascular complications from glabellar intravascular filler injections are major safety concerns. Filler injection into the glabella without precise knowledge of its vascular topography poses a risk of severe complications. METHODS: Computed tomography was used to study 90 cadaveric heads after contrast agent and filler injection, and 15 cadaveric heads were dissected. RESULTS: Central (CAs), paracentral (PCAs), and reverse dorsal nasal arteries (rDNAs) were found in 70 (38.9%), 58 (32.2%), and 16 (8.9%) of the 180 hemifaces, respectively. Based on the presence of CAs, PCAs, and rDNAs between the bilateral supratrochlear arteries (STAs), glabellar arteries were categorized into two main patterns: in type 1 [without named arteries between bilateral STAs; 22 of 90 (24.4%)], the glabella was supplied by bilateral STAs and their branches; in type 2 [with named arteries between bilateral STAs; 68 of 90 (75.6%)], the glabella was supplied by bilateral STAs and CAs, PCAs, and rDNAs. Type 2 could be further divided into three subtypes: in type 2a [45 of 90 (50.0%)], the glabella was supplied by bilateral STAs and one of the named arteries; in type 2b [21 of 90 (23.3%)], the glabella was supplied by bilateral STAs and two of the named arteries; and in type 2c [two of 90 (2.3%)], the glabella was supplied by bilateral STAs and unilateral CA, PCA, and rDNA. CONCLUSION: This study elucidated novel arterial systems and proposed considerations for glabellar filler injection.

Early division of the paramedian forehead interpolated flap using cutaneous ultrasound.

BACKGROUND AND OBJECTIVES: The paramedian forehead flap is an interpolated flap, consisting of the transfer of tissue from the forehead region to the nasal area, irrigated by the supratrochlear artery. Traditionally, the vascular pedicle is divided at between 14 and 21 days. However, this time could be overestimated. Our objective is to demonstrate that the paramedian forehead flap can be divided before that set out in the literature and to demonstrate the usefulness of cutaneous ultrasound to determine the optimal time for division. PATIENTS AND METHODS: A prospective observational study, including patients who required nasal defect reconstruction with a paramedian forehead flap, was designed. The inclusion criteria were: nasal tip, dorsum or alar skin defects following oncological surgery, larger than 2 cm. Twelve patients were included. A retrospective cohort was used to perform a cost reduction analysis. RESULTS: The average time to flow, measured by ultrasound, was 6.6 days. The average number of days to division of the pedicle was 6.9 days. No serious complications were reported. CONCLUSIONS: The paramedian forehead flap can be divided before the traditional reported time. Ultrasound is a reliable and cost-effective technique to determine and individualize pedicle division time.

Evaluation of supratrochlear artery depth and course variations by Doppler ultrasonography along the glabellar frown lines for safer filler injections.

PURPOSE: Hyaluronic acid (HA) injection is a popular nonsurgical, rejuvenating procedure to treat glabellar frown lines, which has devastating complications such as blindness and skin necrosis due to the arterial occlusion of supratrochlear artery (STA). Therefore, when injecting into the frown lines, knowledge of the STA's depth and plane is necessary to prevent possible adverse events. The aim of this study was to identify the depths of STA in the area of the frown lines in order to maximize safety during filler injections. METHODS: Supratrochlear artery depth measurements were performed at the level of eyebrow and at the level of 1.5 cm above the eyebrow. Superficial duplex Doppler ultrasonography was performed of 71 cases. RESULTS: In the eyebrow level, the epidermis-artery distance (EAD) is between 1,8 and 5.9 mm, and the artery-periost distance (APD) is between 0.7 and 3.7 mm. In the 1.5 cm superior level of the eyebrow, the EAD is between 1.8 and 5.1 mm and the APD is between 0.6 and 3.8 mm. There was no significant difference between the depth measurements of the right and left STA. At the eyebrow level, APD is greater in men than in women. As the body mass index increases, the EAD and APD depth increases. EAD depth increases with increasing age. CONCLUSIONS: Based on the findings of this study, safe filler injections to correct the glabellar frown lines can be possible with intradermal injections just below the ryhtide. In the glabellar region, subcutaneous and supraperiosteal injections seems to be risky.

Upper Facial Anastomoses Between the External and Internal Carotid Vascular Territories - A 3D Computed Tomographic Investigation.

BACKGROUND: Facial regions with a high risk for causing injection-related visual comprise are dual-supply vascular areas such as the nose, glabella, and forehead. These regions have in common that they receive arterial blood supply both by branches of the internal (ICA) and the external carotid artery (ECA). OBJECTIVE: The authors sought to investigate the anastomotic pathways between ICA and ECA branches in the upper face. METHODS: Postmortem computed tomographic angiographic scans of n = 38 Chinese non-embalmed hemifaces (25 males, 13 females; mean age, 37.79 [11.8] years; mean BMI, 21.90 [2.3] kg/m2) were conducted. Data analysis relied on the calculation of depth, distances, and pathways of forehead and temporal arteries to investigate the number of anastomotic connections, the connecting branches, and the layer of connection between ICA and ECA territories. RESULTS: Between ICA and ECA territories, only 1 connection in 57.9%, 2 connections in 31.6%, 3 connections in 5.3%, and 4 and 5 connections in 2.6% each were identified. A superficial connection was observed in 15.8% whereas in 84.2% the anastomotic connection was identified to be both superficial and deep. CONCLUSIONS: Adverse events following facial minimally invasive soft-tissue filler injections for aesthetic purposes are not frequent but devastating if they occur. Anatomic knowledge as presented in this study can help to increase awareness of 3-dimensional vascular anastomotic pathways and identify safer injection zones and safer fascial planes. Evidence-based injection techniques should be followed, and safety aspects should be placed over the aesthetic outcome.

Three-Dimensional Computed Tomographic Study of the Supratrochlear Artery and Supraorbital Artery to Determine Arterial Variations and Their Relationship.

BACKGROUND: The forehead has high risks associated with filler injection considering its highly complex vascular system. This study aims to thoroughly describe the anatomical variations and relationships between the supratrochlear artery (STA) and supraorbital artery (SOA). MATERIALS AND METHODS: We studied 56 cadaveric heads by computed tomography after contrast-agent injection. RESULTS: The deep branch of the STA originated in the deep superior orbital arcade and the ophthalmic artery (OA), whereas that of the SOA originated at 3 locations: the deep superior orbital arcade, deep superior orbital artery, and OA. The superficial branch of the STA also had 3 origins: the superficial superior orbital arcade, OA, and angular artery, whereas the superficial branch of the SOA had 2 origins: the superficial superior orbital arcade and OA. Based on the relationship between the STA and SOA, 2 main arterial distribution patterns were observed in both superficial and deep layer arteries: STA/SOA connected pattern and STA/SOA disconnected pattern, of which the latter pattern has 3 subtypes. CONCLUSION: The forehead arteries have complex origins. The relationship of the supratrochlear and supraorbital arteries could be categorized into 2 main patterns. The study elucidated the complexity of the forehead vasculature.

Use of Indocyanine Green Angiography to Identify the Superficial Temporal Artery and Vein in Forehead Flaps for Facial Reconstruction.

ABSTRACT: The superficial temporal artery (STA) frontal branch flap is susceptible to venous congestion because of its unpredictable and variable outflow. The authors applied indocyanine green angiogra-phy in identifying the superficial temporal vessels to help surgeons with proper flap designs to avoid severe complications. A retrospective review from 2015 to 2020 was conducted. All the patients who underwent indocyanine green angiography before forehead flap transfer for facial defect reconstruction were reviewed. The STA and vein were observed using indocyanine green angiography preoperatively. The relationship between the artery and vein was investigated. The venous anatomy was analyzed to guide the pedicle design. The survival of the flap and complications were assessed. A total of 12 patients were identified and included in this study. Indocyanine green angiography allows clear visualization of the detailed anatomy of the STA and vein. The frontal branch of the vein had great variations and generally diverged from the arterial branch. The tiny venae comitantes provided sufficient drainage for 2 small forehead flaps. The frontal branch of the vein entered the forehead and was used as the outflow channel in 4 patients. The parietal branch of the vein, which consistently gave off secondary tributaries to the superior forehead, was included in the pedicle in 6 patients. All flaps survived without complications. indocyanine green angiography provided accurate localization of the superficial temporal vessels. This technique may be helpful in the precise planning forehead flap surgeries and in avoiding the risk of venous congestion.

Topographic Anatomy of the Zygomatico-Orbital Artery: Implications for Improving the Safety of Temporal Augmentation.

BACKGROUND: Anatomical knowledge of the zygomatico-orbital artery and its most relevant clinical applications is essential for ensuring the safety of filler injection into the temporal region. The purpose of this study was to provide the precise position, detailed course, and relationship with surrounding structures of the zygomatico-orbital artery. METHODS: Fifty-eight patients who underwent head contrast-enhanced three-dimensional computed tomography and 10 fresh frozen cadavers were investigated. RESULTS: The zygomatico-orbital artery was identified in 93 percent of the samples in this work. Ninety-four percent of the zygomatico-orbital arteries derived directly from the superficial temporal artery, and the remaining arteries started from the frontal branch of the superficial temporal artery. According to the origin of the zygomatico-orbital artery, it was classified into type I and type II. Type I arteries were then classified into three subtypes. The trunk of the zygomatico-orbital artery was located between the deep temporal fascia and the superficial temporal fascia. Deep branches of the zygomatico-orbital artery pierced the superficial layer of the deep temporal fascia. The zygomatico-orbital artery originated from 11.3 mm in front of the midpoint of the apex of the tragus, and most of its trunks were located less than 20.0 mm above the zygomatic arch. The mean diameter of the zygomatico-orbital artery was 1.2 ± 0.2 mm. There were extensive anastomoses between the zygomatico-orbital artery and various periorbital arteries at the lateral orbital rim. CONCLUSION: The precise anatomical knowledge of the zygomatico-orbital artery described in this study could be helpful for cosmetic physicians for improving the safety of temporal augmentation.

Time-domain diffuse correlation spectroscopy (TD-DCS) for noninvasive, depth-dependent blood flow quantification in human tissue in vivo.

Monitoring of human tissue hemodynamics is invaluable in clinics as the proper blood flow regulates cellular-level metabolism. Time-domain diffuse correlation spectroscopy (TD-DCS) enables noninvasive blood flow measurements by analyzing temporal intensity fluctuations of the scattered light. With time-of-flight (TOF) resolution, TD-DCS should decompose the blood flow at different sample depths. For example, in the human head, it allows us to distinguish blood flows in the scalp, skull, or cortex. However, the tissues are typically polydisperse. So photons with a similar TOF can be scattered from structures that move at different speeds. Here, we introduce a novel approach that takes this problem into account and allows us to quantify the TOF-resolved blood flow of human tissue accurately. We apply this approach to monitor the blood flow index in the human forearm in vivo during the cuff occlusion challenge. We detect depth-dependent reactive hyperemia. Finally, we applied a controllable pressure to the human forehead in vivo to demonstrate that our approach can separate superficial from the deep blood flow. Our results can be beneficial for neuroimaging sensing applications that require short interoptode separation.

Endovenous Thermal Ablation of Prominent Central Forehead Veins (Supratrochlear Veins).

BACKGROUND: Many patients complain of prominent vertical veins in the center of their forehead, worse when smiling, wrinkling the forehead in bright light, leaning forward, and when vasodilated in heat, when exercising, or with alcohol. Previous attempts to treat these with external laser, sclerotherapy, and phlebectomy have not been successful. OBJECTIVE: To describe a new method of treating prominent vertical forehead veins and to report the early results. MATERIALS AND METHODS: We used endovenous laser ablation with a 1470 nm diode laser in 15 patients (F:M 12:3; mean age 38.4 years range 24-69). A bare fiber was used once and a 400-µm single ring radial fiber (Biolitec, Vienna, Austria) in all other cases. Tumescence was placed around the vein and a power of 2 to 3 W with a pullback of 7 to 10 seconds per centimeter. RESULTS: Twelve of the 15 patients (80%) ended up with a good cosmetic result and were satisfied, although 2 needed redo treatment. One patient had minor skin tethering, and 2 (13%) suffered burns-one was the only bare fiber case and the other, the only one where 4 W was used. CONCLUSION: We present a novel technique to treat prominent vertical forehead veins, with apparently good early results.

Tomography of the Forehead Arteries and Tailored Filler Injection for Forehead Volumizing and Contouring.

BACKGROUND: The forehead is a challenging area for filler injection because of the risk of serious complications. Anatomy-based filler injection techniques help to avoid severe vascular complications. MATERIALS AND METHODS: Sixty-six cadaver heads were infused with adequate lead oxide contrast through the external carotid arteries, internal carotid arteries, facial artery, and superficial temporal artery. Three-dimensional computed tomography scans were reconstructed using validated algorithms. We measured the length and arc length of "beautiful" foreheads evaluated by 3 skilled surgeons. RESULTS: The frontal branch of the superficial temporal artery (FBSTA) was classified based on the main trunk as follows: Type I FBSTA (89.72%) took a sudden turn (89.56° ± 11.76°) once passing through the temporal crest, whereas Type II FBSTA (10.28%) barely turned (52.26° ± 6.81°) at the temporal crest. A total of 319 arteries passed through the midline in 48 cadaver heads. There were more superficial arteries (292 of 319) than deep arteries (27 of 319). The difference in the length and arc length of the forehead was 19.66 ± 4.35 mm. CONCLUSION: This study introduces an effective technique for forehead filler injection that minimizes the risk of filler injection and improves patient satisfaction.

Localization and Topography of the Arteries on the Middle Forehead Region for Eluding Complications Following Forehead Augmentation: Conventional Cadaveric Dissection and Ultrasonography Investigation.

Forehead augmentation with filler injection is one of the most dangerous procedures associated with iatrogenic intravascular injection resulting in the severe complications. Nonetheless, few studies have determined the explicit arterial localization and topography related to the facial soft tissues and landmarks. Therefore, this study aimed to determine an arterial distribution and topography on the middle forehead region correlated with facial landmarks to grant an appropriate guideline for enhancing the safety of injection. Nineteen Thai embalmed cadavers were discovered with conventional dissection and 14 Thai healthy volunteers were investigated with ultrasonographic examination on the middle forehead. This study found that at the level of mid-frontal depression point, the transverse distance from the medial canthal vertical line to the superficial and deep branches of supraorbital artery were 9.1 mm and 15.1 mm, respectively. Whereas the depths from the skin of these arteries were 4.1 mm and 4.3 mm, respectively. Furthermore, the frontal branch of superficial temporal artery was detectable in 42.1% as an artery entering the forehead area. At the level of lateral canthal vertical line, the vertical distance of frontal branch was 31.6 mm, and the depth from skin of the artery was 2.7 mm. In conclusion, a proper injection technique could be performed based on an intensive arterial distribution and topography, and ultrasonographic examination before the injection is also suggested in order to restrict the opportunity of severe complications.

Anatomical and Ultrasonography-Based Investigation to Localize the Arteries on the Central Forehead Region During the Glabellar Augmentation Procedure.

Glabellar augmentation is one of the most popular cosmetic procedures but can entail severe complications caused by inadvertent intravascular injection of filler. Nevertheless, few studies have investigated the arteries on the glabellar and central forehead regions. The aim of this study was to correlate the topography and location of the arteries in this area with anatomical landmarks to propose a safety guideline. Two methods were used to investigate the glabellar and central forehead areas: dissection of 19 Thai embalmed cadavers, and ultrasonographic examination of 14 healthy Thai volunteers. At the level of the glabellar point, the horizontal distances from the midline to the arteries were 4.7 mm (central artery), 7.8 mm (paracentral artery), and 14.7 and 19.2 mm (superficial and deep branches of supratrochlear artery). The depths from the skin of the arteries were 3.1 mm (central artery), 4.8 mm (paracentral artery), and 4.2 and 5.9 mm (superficial and deep branches of supratrochlear artery). The periosteal artery was detected in 71.1% as a branch of either the superior orbitoglabellar or the supratrochlear artery. It ran in the supraperiosteal layer for a short course and penetrated the periosteum above the superciliary ridge or above the medial eyebrow, adhering tightly to the bony surface. This study suggests a safe injection technique for the glabella based on a thorough knowledge of arterial distribution and topography and color Doppler ultrasonographic examination prior to the injection, which is recommended to minimize the risk of severe complications. Clin. Anat. 33:370-382, 2020. © 2019 Wiley Periodicals, Inc.

Nasal Reconstruction With Two Stages Versus Three Stages Forehead Fap: What is Better for Patients With High Vascular Risk?

In nasal reconstruction, it is necessary to replace all anatomic layers in order to reinstate correct aesthetics. The most apt donor site to use in order to cover the nose has been recognized as forehead skin. Traditionally 2 phases are required to reconstruct the forehead flap; however, an intermediate third phase was described by Millard which is between transfer of the flap and division of the pedicle. These methods will be compared in this study with regard to both complication rates and aesthetic results in high vascular risk patients.46 patients were enrolled in the study, all of whom were undergoing either total or subtotal nasal reconstruction from January 2001 to March 2018. The 2-step technique (2S Group) was performed on 30 patients and the 3-step technique (3S Group) was performed on 16. Evaluation questionnaires were completed by patients and a plastic surgeon who was extraneous to the study to evaluate aesthetic satisfaction. Complications other than flap necrosis such as infection, wound dehiscence and hematoma were recorded. VAS and Likert mean values, used to evaluate aesthetic satisfaction, were examined with a Student t test and were discovered to be relevant. Complication rates studied with Fisher exact test showed no statistically significant difference between the 2 groups. The 3-phase method for nose reconstruction using a forehead flap represents a better functional and aesthetic option for patients at high vascular risk.

Basal Cell Carcinoma Arising over a Venous Malformation of the Forehead Communicating with the Endocranial Veins.

INTRODUCTION: An increasing number of skin cancer arising over vascular anomaly has been reported in literature. In such cases, the oncologic radicality required to threat skin malignancies may be in contrast with the safety needed when dealing with vascular malformation. As a result, treatment of this association may be insidious and treacherous and imposes a sound knowledge and carefulness. MATERIALS AND METHODS: The authors report on a case of a 77-years-old woman affected by a basal cell carcinoma (BCC) arising over a vascular malformation of forehead. Preoperative radiological imaging revealed an underlying venous malformation (VM) communicating with intracranial district. Patient underwent sclerotherapy of the VM with gelified ethanol in order to reduce potentially fatal bleeding during surgery and, on the other hand, any leakage of the sclerosant in the intracranial veins. Excision of the BCC was then performed without complications. RESULTS: Neither intra-operative nor post-operative complications were observed. Current 3-years follow-up shows no recurrence of BCC whilst the residual VM is stable and clinically silent. CONCLUSIONS: Mechanisms leading to the onset of skin cancers over venous malformations are still unclear. However, association between these 2 conditions may be underestimated with possible catastrophic consequences. Thorough knowledge of vascular malformations and a multidisciplinary approach is of the uttermost importance when dealing with such clinical challenges.

Experience of Replantation and Reconstruction in Total Scalp, Partial Forehead, and Ear Avulsions.

In this study, the authors present the challenges of replantation and management of 2 patients who have total scalp, partial forehead and ear avulsion. A 39-year-old male farmer was admitted to the emergency room with the total scalp, forehead, partial right eyebrow and upper eyelid amputation after his hair was catched by an agricultural machine. Anastomoses of 2 arteries and 2 veins in the occipital region were done first. Anastomosis of the right and left superficial temporal arteries and veins were performed end to end by turning the operating table without moving the head, followed by 1 vein anastomoses in the frontal region. Although anastomotic blood flow was observed by Doppler ultrasonography, there were changes suggesting necrosis in the frontal and both temporoparietal regions and later in the occipital region. Necrotic tissues began to be debrided tangentially from the 10th day. During serial debridement, it was observed that the necrotic tissue includes skin and connective tissue. At the end of the post-operative second month, surgical treatment was completed and 12 months after the surgery, the patient lives with the wig because of hair loss, but the patient is cosmetically satisfied. An 18-year-old female gatherer was admitted to the emergency room with the total scalp, both eyebrows, right upper eyelid and partial right ear avulsion, after her hair was catched by an agricultural machine. Totally, anastomoses of 4 arteries and 3 veins were performed. On the 10th post-operative day, necrotic skin findings appeared and serial debridement were performed and it was revealed that aponeurosis was fully intact. The defect areas of skin and connective tissue were repaired with STSG. Intact partial temporal scalp tissue was present. Scalp replantation should always be considered as the first choice, according to the similar tissue principle of tissue repair in plastic surgery if there is no contraindication. Additionally, performing multiple arterial and vein anastomoses, evaluating the patient position in the post-operative period for anastomosis and hemodynamic follow-up, avoiding aggressive debridement and early reconstruction may give the patient the chance of skin grafting which is the basis of the reconstructive ladder.

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol.

Photoplethysmography (PPG) signals from the forehead can be used in pulse oximetry as they are less affected by vasoconstriction compared to fingers. However, the increase in venous blood caused by the positioning of the patient can deteriorate the signals and cause erroneous estimations of the arterial oxygen saturation. To date, there is no method to measure this venous presence under the PPG sensor. This study investigates the feasibility of using PPG signals from the forehead in an effort to estimate relative changes in haemoglobin concentrations that could reveal these posture-induced changes. Two identical reflectance PPG sensors were placed on two different positions on the forehead (above the eyebrow and on top of a large vein) in 16 healthy volunteers during a head-down tilt protocol. Relative changes in oxygenated ( Δ HbO 2 ), reduced ( Δ HHb) and total ( Δ tHb) haemoglobin were estimated from the PPG signals and the trends were compared with reference Near Infrared Spectroscopy (NIRS) measurements. Also, the signals from the two PPG sensors were analysed in order to reveal any difference due to the positioning of the sensor. Δ HbO 2 , Δ HHb and Δ tHb estimated from the forehead PPGs trended well with the same parameters from the reference NIRS. However, placing the sensor over a large vasculature reduces trending against NIRS, introduces biases as well as increases the variability of the changes in Δ HHb. Forehead PPG signals can be used to measure perfusion changes to reveal venous pooling induced by the positioning of the subject. Placing the sensor above the eyebrow and away from large vasculature avoids biases and large variability in the measurements.